Production of tobacco-smoke filters

ABSTRACT

The invention concerns a method of producing, in a continuous manner, tobacco-smoke filters each comprising a tube of porous tobacco-smoke filter material blocked at one end by a plug of smoke-impermeable material. Lengths of the plug material are deposited automatically upon a strip of the filter material at predetermined intervals along the same and the strip is brought to the form of the tube around the plug lengths. In the case of filters each further comprising an outer smoke-impermeable tubular wrapper disposed around the said tube with a gap between them which is closed at the other end of the tube, the tubular wrapper is automatically applied to and formed over the assembly consisting of the tube and plug lengths.

United States Patent [19] Luke [ 1 PRODUCTION OF TOBACCO-SMOKE FILTERS [75] Inventor: John A. Luke, Southampton,

England [73] Assignee: Brown & Williamson Tobacco Corporation, Louisville, Ky.

22 Filed: Mar. 8, 1972 21 Appl. No.: 232,669

[30] Foreign Application Priority Data Mar. 12, 1971 Great Britain 6693/71 [51] Int. Cl B31f l/00 [58] Field of Search 131/l0.5, 261 B, 11, 10.7

' 13l/10.9; 93/1 C, 77 FT; 156/199, 200, 201,

[ Dec. 17, 1974 Primary ExaminerCharles E. Van Horn Assistant Examiner-David A. Simmons Attorney, Agent, or Firm-Finnegan, Henderson, Farabow & Garrett 5 7] ABSTRACT The invention concerns a method of producing, in a continuous manner, tobacco-smoke filters each comprising a tube of porous tobacco-smoke filter material blocked at one end by a plug of smoke-impermeable material. Lengths of the plug material are deposited automatically upon a strip of the filter material at predetermined intervals along the same and the strip is brought to the form of the tube around the plug lengths. In the case of filters each further comprising an outer smoke-impermeable tubular wrapper disposed around the said tube with a gap between them which is closed at the other end of the tube, the tubular wrapper is automatically applied to and formed over theassembly consisting of the tube and plug lengths.

14 Claims, 15 Drawing Figures PATENTEI] DEC 1 71974 sum 1 DE 6 FATENTED DEC 1 71974 SHEET 2 OF 6 PATENTED DEC] 7 I974 S'rliET 5 OF 6 PRODUCTION OF TOBACCO-SMOKE FILTERS This invention concerns the production and assembly of tobacco-smoke filters from two or more components, particularly but not exclusively filters comprising a porous filter tube of smoke-filter material which extends longitudinally within and spaced from an outer smoke-impermeable tubular wrapper and is blocked by a smoke-impermeable plug at one end, while the space between the wrapper and the tube is blocked at the other end.

It is an object of the invention, to provide a method and apparatus by which tobacco-smoke filters, especially cigarette filters, can be produced reliably and at high speed by simple means.

According to the invention, in a method of producing, in a continuous manner, tobacco-smoke filters each comprising a tube of porous tobacco-smoke filter material blocked at one end by a plug of smokeimpermeable material, lengths of the plug material are deposited automatically upon a strip of the filter material at predetermined intervals along the same and the strip is brought to the form of the tube around the plug lengths.

For producing filters each further comprising an outer smoke-impermeable tubular wrapper disposed around the said tube with a gap between them which is closed at the other end of the tube, the tubular wrapper may be automatically applied to and formed over the assembly consisting of the tube and plug lengths.

The plug lengths are advantageously produced either by severing them from a rod of the plug material or as a string of interconnected plug lengths.

The wrapper is preferably either formed around the assembly of filtertube and plug'lengths by extrusion in v a cross-head die or is produced by bringing together preformed longitudinal sections of wrapper around the said assembly.

Examples of ways in which the invention can be carried into effect will now be more fully described with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are a longitudinal section and end view to an enlarged scale of a filter whose production is to be described,

FIGS. 3 and 4 are diagrammatic side and plan views of one form of apparatus used in the production of such filters,

FIG. 5 is a side elevation to a larger scale of a component device of that apparatus, serving for producing lengths of plug material and depositing them on a filterpaper strip,

FIG. 6 is a horizontal section of a cross-head die for forming and applying a wrapper around an assembly of filter-paper tube and lengths of plug material,

FIG. 7 is a diagrammatic side elevation, to a larger scale than FIGS. 1 and 2, of a sealing component,

FIG. 8 is a detail end view of a side-heating device of that component,

FIG. 9 is a detail side view of a centre-heating device thereof,

FIG. 10 is a perspective view of a half-section of wrapper to be applied in another manner,

FIG. 11 is a diagrammatic side view of part of an apparatus operating in the manner last referred to, and

FIGS. l2, l3, l4 and are, respectively, a front elevation, plan view, a section of the line XlV-XIV and a section on the line XVXV in FIG. 12 of another form of component for producing lengths of plug material.

A single cigarette filter which can be produced by apparatus to be described is shown in FIGS. 1 and 2. It consists of a tube 1 of smoke-filter paper located coaxially within a tubular casing 2 made of a substantially smoke-impermeable plastics or other softenable material, such as polyethylene, polypropylene, ethylene vinyl acetate copolymer, polyvinyl chloride, polystyrene, cellulose acetate or the like. Suitably, it is made of polyethylene. The tube 1 is located and supported in the wrapper 2 by longitudinal internal ribs 3 formed integrally with the latter at intervals around its circumference. At the mouth end of the filter, the interior 4 of the tube 1 is closed by a short cylindrical or disc-shaped plug 5 of substantially smoke-impermeable plastics material such as extruded, solid or foamed, polyethylene, polypropylene, ethylene vinyl acetate copolymer, nylon, polyurethane or cellulose acetate, for instance a white cellulose acetate rendered impermeable by the use of a high concentration of plasticizer. Suitably it is made of polyethylene. At this end, the relatively narrow annular space 6 between the tube 1 and wrapper 2 is open. At the other end, adjacent to the tobacco rod of the cigarette (not shown), the interior 4 of the tube 1 is open, whereas the annular space 6 is closed by an inturned lip 7 on the wrapper 2. As hereinafter described, such a lip may be produced and sealed to the tube by the application of heat. However, the seal may be assisted by adhesive, for example, a polyvinylacetate adhesive.

In the filter-producing apparatus to be described, the filters are produced initially, as is commonly done, in lengths providing four such filters, which are'subsequently cut into single filters.

Referring now to FIGS. 3 and 4, a strip 10 of filter paper for the tube 1 is supplied from a bobbin ll, plastics-rod material 12 for the plugs 5 from a reel 13, plastics material for the wrapper 2 from an extruder press 14 and, if required, paper strip 15 for a conventional outer filter wrapping from a bobbin 16.

From the bobbin 11, the strip 10 is fed through an applicator 17 by which both edges of the strip 10 are provided with heat-activatable adhesive for the eventual production of a longitudinal tube seam. The strip 10 then passes through a cooler 18, which renders the adhesive inactive, to a device 19 for cutting predetermined lengths Sa, equal to the length of two plugs 5, of plug material from the rod 12 and placing them on the strip 10 at predetermined intervals. For example, for the case of a filter 20 mm long, the lengths 5a may be 5 mm and the interval 40 mm.

As shown in FIG. 5, the rod 12 arriving at the device 19 passes between a feed roller 20 with a transversely serrated circumferential surface 21 and a guide roller 22 with a circumferential groove 23 of semicircular cross section. It advances along a groove 24 in an adjustably mounted platform 25 towards the end of which the lengths 5a are cut off from the rod by a rotary knife 26, of a type well known in the cigarette industry, operating in a slot 27 in the platform. Pushed forward by the following rod 12, each severed length 54 is engaged by a transfer wheel 28 and carried through a guide 29 and past an electrically heated block 30 so as to be deposited on the strip 10. In the device 19, the strip 10, carrying the plug-lengths 5a, advances between a roller 31 with a circumferential groove 32 and a plain roller 33.

The rollers 20, 22, knife 26, wheel 28 and rollers 31 and 33 are driven from a common drive shaft at coordinated speeds so as to produce the predetermined lengths a of plug material and to deposit them at the predetermined intervals on the strip 10. Separation of the lengths 5a is achieved by driving the wheel 28 with a higher peripheral speed than that of the rollers 20, 22. The heated block serves to activate heat-activatable adhesive with which the rod 12 is precoated, so that the plug lengths 5a adhere to the strip 10 where theyare deposited.

If required, the rod 12 may be supplied directly from an extruder to the device 19. Also the several plug lengths 5a may alternatively be placed individually on the paper strip 10 at the predetermined intervals by means of a rotating horizontal finger wheel of conventional type.

The paper strip 10 carrying the lengths Ba of plug material next progresses through a forming unit 34 (FIGS. 3 and 4) in which it is brought'to tube form around the said lengths and a heated sealing unit 35 by which the edges of the strip are sealed together and the plug lengths are sealed to the tube, followed by a caterpillar.

traction unit 36. The units 34 to 36 may be of known kind such as are used for producing tubular paper wrappings in cigarette-making or filter-making machines. Advantageously, however, the units 34 and 35 are devised to form the tube with a butt joint rather than a lap joint.

The assembly 10a thus produced and consisting of the strip 10 wrapped as a tube around the plug lengths 5a is next supplied by means of an extruder cross-head die 37 with a tubular casing of plastics material which provides the casing'2 of the eventual filters. Such a die is illustrated by FIG. 6. The plastics material is supplied under pressure from the press -14 through a feed duct 38, a divided, tapering, distribution duct 38' extending forwardly around a nozzle carrier 39 and annular passages 40, 40' to an annular die outlet 41 formed between an outer nozzle element 42 and an inner nozzle element 43. The tubular assembly 10a passes co-axially through the die by way of bores 44,44 leading to the outlet 45of the nozzle element 43. The plastics material is thus extruded co-axially around the tube. To

, which affords accurate guidance just before the extrusion point, and to provide a cooling effect there. The ribs 3 (FIGS. 1 and 2) are produced by longitudinal grooves formed at 46 in the outside surface of the nozzle element 43. The nozzle element 42 can be accurately centred in relation to the element 43 by means of a plurality of radial centring screws, one of which is seen at 47. The die body is heated by electrical elements, one of which is seen at 48.

The extruded assembly 10b (FIGS. 3 and 4) then passes, with orwithout an outer wrapping strip 15, into a garniture 49. If a strip 15 is not wrapped around the assembly 10b, the garniture 49, which may be of the kind well known in the cigarette industry, serves mainly as a haul-off device by the action of the customary garniture tape. If an outer wrapping strip 15 is provided, the garniture serves also to form the strip around the assembly 10b and to consolidate the whole assembly. Housed with the garniture is a cut-off device, operative at 50, which divides the assembly 10b midway between alternate, not consecutive, pairs of plug lengths 5a. For the case of the above example of filters 20 mm long, the assembly 10b is therefore divided into 80 mm lengths 10c, each including two double-plug lengths 5a each situated at 20 mm from the respectively adjacent cut end. Each length 10c thus comprises material for four single-filter lengths. The division at 50 into four-filter lengths, 10c, is effected at the open ends (i.e., at the ends opposite to the plug lengths 5a) of the two outer single-filter lengths; Division into single-filter'lengthsis effected at a later stage, for example in known manner during the assembly of filter tip cigarettes incorporating the filters.

The cut-ofi lengths 100 are supplied singly to a chain conveyor 51 (FIG. 7) by which they are advanced under a centreline electrical heater 52 (FIG. 9) with a blunt knife edge 59 which pressed in to the depth of the casing 2 with its ribs 3 to deform the casing material into the paper tube 1 to produce the seals 7 of the two inner single filters and past electrical-heaters 53(FIG. 8) at each side for similarly producing the seals 7 of the two outer singlefilters. The lengths 106 are deposited singly upon and transversely of a conveyor band 54 feeding the conveyor 51. The latter comprises a pair of endless chains 55 each supporting a series of spaced carrier blocks 56 which hold the lengths 10c freely near the ends, but with some overhang (FIG. 8), in recesses 57. The lengths 100 are carried along by the chains 55 in light contact with a fixed plate 58 so that they are caused to roll in the recesses 57 throughout the operative upper flight of the conveyor 51 and, in passing under the heater 52, are provided with the two inner seals 7 as already described. The edge 59 does not sever the length 100, the tube 1 being left uncut. As

. shown in FIG. 8, each side heater53 has a heating rib 60 with a narrow flat edge 61 which presses in the casing material to produce the seal 7 of the filter at that end of the length 10c. The filter-rod lengths 10c are finally discharged from the carriers 56 at 62.

In an alternative method of producing the wrapper 2, two strips of the plastics material are extruded, each in the cross sectional form (FIG. 10) of half the casing 2 with flange-like flash 63 at the edges. The two extruded formations 64,65 (FIG. 11) 'arebrought together, in mirror-image fashion, around a filter-paper tube 10a, into which plug lengths 50 have already been introduced in the manner described above, between heated rollers 66 having peripheral grooves 67. The formations 64,65 are thereby shaped around the tube 10b and sealed together. The flash 63 is removed by rotating'knives 68 co-operating with rollers 69. The resultant tubular assembly 10b may then be dealt with in the manner described above. The two formations 64,65 could alternatively be sealed together by the use of adhesive.

According to another method of producing the easing 2, in which the ribs 3 are provided by a number of continuous strips, approximately /& mm wide, of a plastics material, stiff paper or a resin wax which are fed in transversely spaced relation longitudinally onto a tape of smoke-impermeable paper already carrying an assembly, comprising a paper tube and plug lengths, such as 10a. The whole assembly is then passed through a garniture, such as is used in a conventional cigarettemaking machine, whereby the tape is wrapped around the paper tube so that the said strips form longitudinal supporting ribs similar to the ribs 3. In the gamiture, the longitudinal edges of the tape are also joined together in known manner. Annular internal ribs or projections equally spaced longitudinally of the assembly may be provided in similar manner.

Such ribs may also be provided by discontinuous series of strips separated by lengths equal to the plug lengths. Strips may be laid so as to form helical ribs. Strips may be formed integrally with a transverse strip which is brought to a circular shape to serve as a seal between the wrapper and the tube.

Projections for supporting the filter tube may be formed on an intermediate tubular element to be disposed between the filter tube and an impermeable outer wrapper. Thus, for example, an intermediate element may be produced from a strip of thick paper perforated with longitudinal lines of hole or slots, which may be side by side or staggered. The inwardly deformed margins of the holes or slats serve to space the rest of the element from the filter tube. Instead of being provided with holes or slots, the intermediate element may be formed with inward embossments similarly arranged. The intermediate element may be provided with the holes, slots or embossments all over or in series of lengths interrupted by plain lengths equal to the plug lengths.

Projections may also be formed by granules adherent to the inside of a plain wrapper. For example, a wrapper strip of impermeable paper may be coated on what will be the inside of the wrapper with glue in a predetermined pattern and carbon granules sprinkled on the glue. When the wrapper strip is wrapped around the filter tube, adherent granules will support the filter tube in the wrapper with an annular space between them. The carbon will then also contribute its selective filtering effect to the efficacy of the filter.

According to another method of providing a smoke path equivalent to that formed by the annular gap 6, an assembly comprising a filter tube already containing plug lengths is wrapped with a thicker layer formed from a strip of smoke permeable open-cell foam, foamed paper or low-density paper. This layer is overwrapped with smoke-impermeable paper. The assembly thus produced is cut into filter lengths. A seal equivalent to the seal at 7 in FIG. 1 may be similarly produced or may be provided by a sealing strip applied to the aforesaid layer before it is brought to tubular form in a garniture. Such a sealing strip may be made, say, of paper or card stuck with a polyvinyl acetate, hotmelt or like adhesive or of a plastics material.

Plug-lengths 5a may be produced by methods other than that described above, for example as a string of plug-lengths connected together at the predetermined intervals. In a suitable apparatus for this purpose shown in FIGS. 12 to 15, a rod 70 of the plastics plug material extruded with a diameter slightly greater than that of the plugs 5 is passed in a heated condition first between a pair of shaping wheels 71,72 and then between a pair of trimming wheels 73,74 all of which are driven together and at the same peripheral speed. The wheels 71,72 are identical and are each provided at peripheral distances equal to the predetermined intervals with a series of recesses 75 having bottoms 76 of nearly semicircular shape. Corresponding recesses 75 of the said wheels form rolling moulds by which the plug lengths 5a are brought accurately to shape. Between the recesses are lands 77 which press out the rod 70 to a flattened web formation 78. The wheels 73,74 also have recesses 79, at the same peripheral distances, for accommodating the plug lengths 5a as they pass between the said rolls. Between the recesses 79, there are lands 80, each land of the upper wheel 73 having a sharpedged rectangular rib 81 and that of the lower wheel 74 a complementary groove 82 in which the rib 81 closely engages (FIG. 15). Corresponding lands of the two wheels 73,74 are sufficiently spaced from each other to permit entry of the web formation 78 between them. The rib 81 does not extend to the bottom of the groove 82. During the passage of a flattened rib formation 78 between the wheels 73,74, marginal portions thereof are trimmed off between the sharp co-acting edges of the rib 81 and groove 82, leaving only a narrow web 83 between plug lengths 5a. Marginal portions will also be severed from the plug lengths 5a by the side portions of the sharp transverse edges 84, of the recesses 79, which may also trim-off any irregularities at the ends of the plug lengths 5a. Any flash on the plug lengths themselves will be trimmed off by co-acting sharp edges 85 of the wheel 73 and of side discs 86 of the wheel 74.

Another method of producing a string of plug lengths at the predetermined intervals is by extruding the plastics plug material in a cross-head die around a core composed of a material having a higher melting point than the extrudate and shrinking'the extrudate at the said intervals.

The string of plug lengths produced is fed directly from the device of FIGS. 12-15, from the apparatus just described, or from a reel upon which the string has been stored, and is deposited upon the paper strip 10 before it enters the first forming unit 34 of apparatus similar to that shown in FIGS. 3 and 4, but without the device 19.

An alternative method of producing the seal at 7 (FIG. 1) is by passing the assembly 10b of wrapper, filter tube and plug lengths through a heater which operates to apply heat intermittently so that the wrapper is softened or partially melted to close the annular gap at 7 at the predetermined intervals along the assembly.

According to another method, a wrapper, filter-tube and plug-lengths assembly produced, for example, by the apparatusshown in FIGS. 3 and 4 as far as the garniture 49 is cut, midway of the plug lengths, to form single-filter lengths. The annular gap between the wrapper and filter tube is then closed, by joining to each section, in abutting relationship, a second mouthpiece or second filter section in the form of a tube of plastics material having a wall thickness corresponding to the radial dimension of the gap.

Alternatively, a second, filter section used to close the annular gap may be made of a thermoplastics extruded foam material of open-cell type having a hardened rim whose depth corresponds to the radial dimension of the gap, thus providing a so-called dual filter.

I claim:

1. A method of continuously producing tobacco smoke filter components comprising:

a. depositing lengths of smoke-impermeable plug material upon a strip of filter material at predetermined intervals so that the lengths of plug material are spaced a substantially greater distance apart than their individual lengths;

b. forming a tube of the strip about said plug lengths;

c. disposing an outer smoke-impermeable tubular casing around the tube;

d. providing means between said filter material and said tubular casing to retain at least portions of said casing and filter material in spaced relation to provide a longitudinal smoke flow between said filter material and plug assembly and said smokeimpermeable tubular casing;

e. forming a circumferential seal between said casing and said tube at desired spaced positions from said plugs to prevent the passage of smoke between the casing and tube at the point of said seal; and

f. cutting said tube into individual filter smoke components each having a circumferential seal at one end thereof.

2. The method in accordance with claim 1 wherein the plug lengths are produced in a continuous operation by severing them from a rod of the plug material and depositing the severed lengths at the predetermined intervals upon the strip of filter material.

3. The'method in accordance with claim 1 wherein the plug lengths are produced in a continuous operation by forming them as a string of plug lengths conspace the tube from the casing is formed around the assembly.

10. The method in accordance with claim 1 wherein the assembly consisting of the filter tube and plug lengths is passed together with an outer casing through a garniture.

11. The method in accordance with claim 1 wherein the assembly consisting of the filter tube and plug lengths is passed together with an outer casing through a garniture in which the assembly is provided with an outer wrapping.

12. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is formed around the filter tube with a gap therebetween so that the casing and tube are spaced along a substantialportion of their relative lengths, closure of the gap at predetermined intervals being effected by deformation of the casing onto the filter tube by the application of localized heat and pressure.

nected together at the predetermined intervals and the string is deposited upon the strip of filter material with the plug lengths maintained at the said intervals by their interconnection.

4. The method in accordance with claim 1 wherein the plug lengths are produced by a rolling-mold operation including passing the plug material between a pair of opposing wheels having mating recesses at predetermined intervals to form a cavity corresponding to plug length dimensions.

5. The method in accordance with claim 1 wherein the edges of the strip of filter material brought to tubular form around the plug lengths are sealed together.

6. The method in accordance with claim 1 wherein the edges of the strip of filter material brought to tubular form around the plug lengths are sealed together with a butt joint.

7. The method in accordance with claim 1 wherein an outer smoke-impermeable. tubular casing is formed continuously around the assembly consisting of the filter tube and the plug lengths by extruding it in a crosshead die through which the assembly is passed.

8. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is produced continously around the assembly consisting of 13. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is formed around the filter tube with a gap therebetween so that the casing and tube are spaced along substantially their entire relative lengths, closure of the gap at predetermined intervals being effected by rolling lengths of the assembly consisting of the casing, filter-tube and plug lengths past at least one heated member, arranged to engage the assembly with localized pressure.

14. An apparatus for continuously producing tobacco smoke filter components comprising:

a. means for feeding a strip of filter material;

b. means for depositing lengths of smokeimpermeable plug material upon said strip of filter material at predetermined intervals so that the lengths of plug material are spaced a substantially greater distance apart than their individual lengths;

0. means for forming a tube of the strip about said plug lengths;

d. means for disposing an outer smoke-impermeable tubular casing around the tube;

e. means for providing between said filter material and said tubular casing means to retain at least portions of said casing and filter material in spaced relation to provide a longitudinal smoke flow between said filter material and plug assembly and said smoke-impermeable tubular casing;

f. means for forming a circumferential seal between said casing and said tube at desired spaced positions from said plugs to prevent the passage of smoke between the casing and tube at the point of said seal; and

g. means for cutting said tube into individual filter smoke components each having a circumferential seal at one end thereof. 

1. A method of continuously producing tobacco smoke filter components comprising: a. depositing lengths of smoke-impermeable plug material upon a strip of filter material at predetermined intervals so that the lengths of plug material are spaced a substantially greater distance apart than their individual lengths; b. forming a tube of the strip about said plug lengths; c. disposing an outer smoke-impermeable tubular casing around the tube; d. providing means between said filter material and said tubular casing to retain at least portions of said casing and filter material in spaced relation to provide a longitudinal smoke flow between said filter material and plug assembly and said smoke-impermeable tubular casing; e. forming a circumferential seal between said casing and said tube at desired spaced positions from said plugs to prevent the passage of smoke between the casing and tube at the point of said seal; and f. cutting said tube into individual filter smoke components each having a circumferential seal at one end thereof.
 2. The method in accordance with claim 1 wherein the plug lengths are produced in a continuous operation by severing them from a rod of the plug material and depositing the severed lengths at the predetermined intervals upon the strip of filter material.
 3. The method in accordance with claim 1 wherein the plug lengths are produced in a continuous operation by forming them as a string of plug lengths connected together at the predetermined intervals and the string is deposited upon the strip of filter material with the plug lengths maintained at the said intervals by their interconnection.
 4. The method in accorDance with claim 1 wherein the plug lengths are produced by a rolling-mold operation including passing the plug material between a pair of opposing wheels having mating recesses at predetermined intervals to form a cavity corresponding to plug length dimensions.
 5. The method in accordance with claim 1 wherein the edges of the strip of filter material brought to tubular form around the plug lengths are sealed together.
 6. The method in accordance with claim 1 wherein the edges of the strip of filter material brought to tubular form around the plug lengths are sealed together with a butt joint.
 7. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is formed continuously around the assembly consisting of the filter tube and the plug lengths by extruding it in a cross-head die through which the assembly is passed.
 8. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is produced continously around the assembly consisting of the filter tube and the plug lengths by bringing together preformed longitudinal sections of casing around the assembly in substantial conformance with the outer surface of the assembly and sealing together the edges of the sections.
 9. The method in accordance with claim 1 wherein an outer smoke-impermeable wrapper with internal configurations such as ribs which support the assembly consisting of the filter-tube and the plug lengths and space the tube from the casing is formed around the assembly.
 10. The method in accordance with claim 1 wherein the assembly consisting of the filter tube and plug lengths is passed together with an outer casing through a garniture.
 11. The method in accordance with claim 1 wherein the assembly consisting of the filter tube and plug lengths is passed together with an outer casing through a garniture in which the assembly is provided with an outer wrapping.
 12. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is formed around the filter tube with a gap therebetween so that the casing and tube are spaced along a substantial portion of their relative lengths, closure of the gap at predetermined intervals being effected by deformation of the casing onto the filter tube by the application of localized heat and pressure.
 13. The method in accordance with claim 1 wherein an outer smoke-impermeable tubular casing is formed around the filter tube with a gap therebetween so that the casing and tube are spaced along substantially their entire relative lengths, closure of the gap at predetermined intervals being effected by rolling lengths of the assembly consisting of the casing, filter-tube and plug lengths past at least one heated member, arranged to engage the assembly with localized pressure.
 14. An apparatus for continuously producing tobacco smoke filter components comprising: a. means for feeding a strip of filter material; b. means for depositing lengths of smoke-impermeable plug material upon said strip of filter material at predetermined intervals so that the lengths of plug material are spaced a substantially greater distance apart than their individual lengths; c. means for forming a tube of the strip about said plug lengths; d. means for disposing an outer smoke-impermeable tubular casing around the tube; e. means for providing between said filter material and said tubular casing means to retain at least portions of said casing and filter material in spaced relation to provide a longitudinal smoke flow between said filter material and plug assembly and said smoke-impermeable tubular casing; f. means for forming a circumferential seal between said casing and said tube at desired spaced positions from said plugs to prevent the passage of smoke between the casing and tube at the point of said seal; and g. means for cutting said tube into individual filter smoke components each having a circumferential seal at one end thereof. 